OO-623: check more places where authors can create groups as enrolment and contact course building block, visibility access rules and course preview form

OO-467: versions of runstructure, editortreemodel, CoruseConfig.xml + low level max number of versions check

OO-470: merged containers are transient with an init method to initialize them after deserialization

OO-291: avoid groups and areas with the same name if a course is exported with the backward compatibility flag

OO-213: make OpenOLAT more robust against corrupted course, mark them in details view, make home resistant to corrupted courses, give the possibility to delete them

OO-157: optimization of WebDAV, reduce the number of DB queries with lazy loading, specific resolve method, lazy loading of quota...

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branch : bps